The present invention relates to apparatus for remotely monitoring vehicle tire pressure and temperature.
With the increasing replacement costs of pneumatic tires, as well as the service charges and time lost for replacement, it is imperative that the tires be maintained at the proper pressure, to prevent unnecessary wear or high temperatures which may damage the tire. This is especially important for commercial vehicles such as trucks, buses and aircraft. Safety considerations likewise dictate that tires be always maintained at their rated pneumatic pressure.
In the prior art, various systems have been formulated for remotely monitoring the tire pressure and temperature of a motor vehicle. These have generally been provided with pressure and temperature sensors mounted to the wheel valve stem or rim, including a positive temperature coefficient thermistor mounted to the rim for sensing temperature, in U.S. Pat. No. 3,852,717 to Hosaka, and a pair of bellows-type pressure sensors coupled to the valve stem in U.S. Pat. No. 2,860,321, to Strickland. In U.S. Pat. No. 4,067,235 to Markland, a pressure sensor only is shown mounted within the tire. The tire condition information has been transmitted to the vehicle by slip rings or various electromagnetic means. Power for the sensors and transmitter has been provided directly by the vehicle battery, by a complex transponder-type system, such as in the Markland patent, or by a battery, as in U.S. Pat. No. 4,090,172 to Vesnic.